feature: most.create for nodejs style callbacks

Node has the below style of async API for their ecosystem. Seeing the most.create is going to be moved into its own project, can we get a simple/clean way to provide Node async functions to it to create a stream source? e.g. most.fromNodeCallback(myAsync)

function myAsync(val, cb) {
   const err = null;
   const result = "success";
   // do something async
   cb(err, result); // may be called once or multiple times
}

[briancavalier]

@jadbox Now that @partially-applied has created mostify, and @most/create is available as an a la carte package, I feel like there are good solutions out there for now.

So, I’ll close this, but please feel free to continue discussion here.

[briancavalier]

Would native Node support be important enough to put into core?

My first instinct is that it should be a separate package, e.g. @most/node or something fairly obvious like that, but I’m open to discussing it. Browser apps likely wouldn’t need it 90% of the time, so being able to add it to a project a la carte is appealing.

Thoughts?

I’m curious why the Src/Sink method would be faster than most.create?

All most streams make the same guarantee: the function you pass to observe/forEach/reduce will not be called before observe/forEach/reduce returns. There are really two options for making that guarantee in most.create, either 1) wait for the stack to clear before calling the producer function passed to most.create, or 2) buffer events and propagate them after the stack clears.

Originally, it did 1, which proved to be confusing for users, so we switched to 2.

Since node functions already are async (well, they should be anyway!), by their very nature they would not propagate an event before the stack clears. So, there is no need to a lot of the buffering gymnastics that most.create does … it’d just be adding overhead for no reason.

There are a few other more minor factors. For example, most.create creates 3 closures to pass to the producer function. A node solution probably would only need 1. Also, because most.create is a general purpose solution, it has to do more generalized error handling. That means it uses try/catch in several places, which prevents the VM from optimizing several functions.

On the other hand, using Source/Sink directly is more “bare metal”. A node solution with Source/Sink would not need to do buffering, could create fewer closures, and could do error handling in a way that is more tailored to node style functions.